Metal ion centers are a fundamental component of many enzymes and other biological systems. Geometry changes occurring as a result of complex formation between the metal ion and a ligand may be a requirement before conformation changes between the metal ion and a ligand may be requirement before conformation changes can occur in a biological molecule. This proposal will explore the causes of the geometry changes in d-transition metal and f-transition metal systems. The specific aims of this proposal are: (I) When a metal ion reacts with a ligand, is the complex inner sphere or is it an outer sphere complex where the cation and ligand are separated by one or more solvent molecules? II) When a complex form, does the solvent and/or ligand cause a geometry or conformation change? (III) Are those structural changes caused by a shift from a hydrophobic to a hydrophobic environment, a change that can occur in biochemical molecules. In order to investigate these effects; we are proposing a variety of studies, including: (1) The complexation between Eu(III) and amino acids in mixed solvents will be probed using UV-vis and luminescence techniques to get answers about the three specific aims. (2) Will changing from a simple amino acid to dipeptides enhance or hide these effects?) (3) Will thiocyanate complexation with Eu(III) will allow us to differentiate between inner and outer sphere complexes? (4) Does Ni(II) undergo geometry changes under conditions in which Co(II) undergoes a geometry change? How dependent upon ligand are these geometry changes? Does zinc also undergo geometry changes? Does zinc also undergo geometry changes upon complexation? (5) Are the actinides similar to the lanthanides in biochemical systems and can those radioactive materials be taken up the microbes. A variety off experimental techniques will be utilizes to investigate the fundamental properties of metal ion-ligand systems. Among the techniques, luminescence, luminescence lifetimes, NMR and stopped- flow methods are new to our group.